1. Field of the Invention
The present invention relates to a cleaning apparatus for a semiconductor wafer used in the production process of semiconductors and the like. More particularly, the present invention is concerned with an immersion cleaning apparatus which cleans substrates i.e. silicon wafers and the like with immersing them in cleaning liquids.
2. Description of the Related Art
A cleaning system that uses a combination of cleaning fluids such as SPM (Sulfuric acid Hydrogen Peroxide Mix), APM (Ammonium Hydroxide Hydrogen Peroxide Mix), HPM (Hydrochloric acid Hydrogen Peroxide Mix) and HF (Hydrogen Fluoride) is widely used for a pre-cleaning treatment prior to the thermal diffusion oxidation treatment.
Japanese Patent Laid-open No. 2001-44429 discloses an embodiment of such system and methods using APM, HF and H2O2.
According to the above reference, the system includes at least two containers. In one of the containers is a one-bath-type cleaning container cleaning with hydrofluoric acid (HF), rinsing with a purified water and treating with a diluted solution of hydrogen peroxide are carried out, and in the other of the containers, a drying treatment using IPA (Isopropyl alcohol) is carried out.
The above system further includes four containers. One of them is a cleaning container for a first pre-diffusion cleaning using chemical materials for forming chemical oxide films and the other is a cleaning container for a second pre-diffusion cleaning to rinse off the chemical materials with a purified water.
In such a system, silicon wafers are moved from a clean room having a class 1 cleanliness to a wet cleaning apparatus. Then, the silicon wafers are moved into treatment containers in the cleaning apparatus by robot arms, and cleaning or drying processes are carried out, respectively.
After the cleaning and drying processes, the silicon wafers are returned into the clean room. The wet cleaning apparatus cleans 25 wafers at a time through batch processes.
As described above, at least two wet cleaning containers are used for the cleaning and drying processes those of which includes an APS cleaning, a purified water rinse, a hydrogen fluoride (HF) cleaning and an isopropyl alcohol (IPA) drying.
As illustrated in FIG. 6, the one-bath-type cleaning container includes a cleaning container body 120, a tray 130 to receive chemical solutions spilled from the body 120, a chemical solution supply conduit 301 connected to the bottom of the body 120, chemical solution supply lines 181,191,201 connected to the chemical solution supply conduit 301, and a waste solution line 302.
Each of the chemical solution supply line 181, 191, 201 supplies hydrogen fluoride, H2O2 and a purified water, respectively.
The chemical solutions each are supplied through the supply line 181, 191, 201 to a mixer 222 and mixed. The mixed solutions are injected into the cleaning container 120 through inlets at the bottom of the body 121. In the mixer 222, two or more chemical solutions are mixed up in a proper ratio based on a pre-determined concentration conditions.
A substrate i.e., silicon wafer having a large size for producing semiconductors reduces costs of products such as LSIs, since a larger number of products can be obtained from one substrate. Therefore, a larger substrate tends to be used.
It is just a time when a diameter of the wafer handled by semiconductor production equipments is transited from 200 mm to 300 mm. The introduction of those semiconductor production equipments for the wafer having a diameter of 300 mm in semiconductor production lines necessitates an semiconductor-cleaning apparatus corresponding to the wafer having a 300 mm in diameter.
However, mere enlargement of the cleaning apparatus results in a footprint (an occupation space required for installation of the apparatus) consumption. It is necessary that the apparatus has a processing capacity for larger wafers and a smaller footprint.
And also a cleaning apparatus used for cleaning wafers prior to a gate forming process or an oxide film forming process is required to have a higher cleanliness so that fewer residual contaminations such as particles of metals or organic substances remains on the wafer, corresponding to improvement on concentration and miniaturization of LSIs.
Conventionally, an IPA drying process is carried out after a liquid cleaning process. In this case, the residual IPA on the wafers has to be removed after the drying process, since organic substances must be removed prior to the oxide film forming process.